Ray Duffy is a shape-shifter who blended in by becoming a police officer. However, his programming malfunctioned allowing him to develop emotions for his wife Lisa Duffy and son Nate Duffy.
Thomas Jerome Newton approached him to order him to steal James Van Horn's memories. He accepts and encounters Walter Bishop. Walter stabs him and he knocks Walter out before he escapes with Van Horn's short term memory disk and gives the disk to Newton. Newton then orders him to kill his family and tells him he is not supposed to have feelings especially for humans.
Newton then shoots him because of this flaw moments before Newton is pursued by the Fringe Division. ("Do Shapeshifters Dream Of Electric Sheep?")